This invention pertains to fluorinated metal-organic frameworks having internal channels and cavities in a variety of configurations that are capable of adsorbing hydrocarbons, including typical aromatic and aliphatic oil components. The fluorous metal-organic framewords (“FMOFs”) possess fluorine-lined pore surfaces and are superhydrophobic porous materials with high capacity and affinity to C6-C8 hydrocarbons of oil components.
Crystalline porous materials, either with an inorganic or a metal-organic framework (“MOF”), can be used in a range of applications. These include size- and shape-selective catalysis, separations, gas storage, ion-exchange, sensors, and optoelectronics. In particular, stable MOFs with permanent highly-porous channels or cavities have been explored as effective, economic, and safe on-board vehicular gas (hydrogen or methane) storage materials for fuel-cell-driven automobiles. Extensive efforts have been devoted to the rational design and construction of new MOFs with zeolite-like, well-defined, stable and extra large micro or meso pore size channels exhibiting higher or selective gas affinity properties. Pioneered by Yaghi et al., a vast number of organic ligands with a variety of donor groups and over 40 metal cations have been explored in MOF construction (Yaghi, et al. 1995). A few reports on MOFs utilizing non-fluorinated metal triazolates have appeared recently. (Yang, et al. 2004; Zhang, et al. 2004, 2005; Ouellette 2006).
High volumetric capacity is a very significant property for gas storage applications. The U.S. Department of Energy (“DOE”) has established a multi-stage target for hydrogen storage capacity in materials, including those materials intended for fuel cell applications. The DOE's 2010 targets for a hydrogen-storage system are an energy density of 7.2 MJ/kg and 5.4 MJ/L. Energy density refers to the amount of usable energy that can be derived from the fuel system. The figures include the weight and size of the container and other fuel-delivery components not just the fuel. The 2010 values work out to be 6 wt % of hydrogen and 45 kg of hydrogen per cubic meter. For 2015, the DOE is calling for fuel systems with 9 wt % of hydrogen and 81 kg of hydrogen per cubic meter, which is greater than the density of liquid hydrogen (approximately 70 kg/m3 at 20 K and 1 atm). Particularly for H2 storage in automobiles, the volumetric capacity is arguably more important than the gravimetric capacity because smaller heavy cylinders are easier to accommodate in vehicles than larger cylinders even if the latter were lighter than the former. Due to their high porosity, the best metal-organic frameworks known to date have very low densities (e.g., 0.43, 0.51, and 0.62) (Yaghi, et al. 2006; Long, et al. 2006). Therefore, their volumetric densities are always lower than the gravimetric densities.
In attempts to meet the DOE targets, nanostructured carbon materials (e.g. carbon nanotubes, graphite nanofibers, activated carbon, and graphite) and porous metal-organic frameworks have become of interest to researchers as potential hydrogen adsorbents. However, it has been shown that nanostructured carbons have slow uptake, exhibit irreversible adsorption, and contain reduced transition metals as impurities. Meanwhile, the known MOFs have low volumetric H2 uptake due to their low densities and weak affinity to hydrogen molecules. In addition, the porous nature and high surface areas of metal-organic frameworks give rise to rather weak H2 adsorption energies (˜5 kJ/mol). This is why cryogenic temperatures are usually required to observe significant H2 uptake.
Oil and petroleum products (hydrocarbons) are some of the most important energy sources in the world. As long as oil is prospected, transported, stored and used, there be a risk of spillages that may result in significant environmental damage and vast economic loss. It is estimated that the oil spill clean-up costs worldwide amount to over $10 billion dollars annually. The adverse impacts to ecosystems and the long-term effects of environmental pollution by these and other releases call for an urgent need to develop a wide range of materials for cleaning up oil from impacted areas, especially because the effectiveness of oil treatment varies with time, type of oil and spill, location and weather conditions. There are many adsorbents in use for oil spill cleanup, including sand, organo-clays and cotton fibers. These adsorbents, however, have strong affinity to water, limiting their effectiveness in cleanup operations. Therefore, the development of waterproof sorbents that are effective even at very low concentrations of oil residue remains an urgent challenge. The Deepwater Horizon oil spill devastation in the Gulf of Mexico has raised awareness and urgent need for water-stable and waterproof sorbent materials that can completely and effectively clean up the oil residue present in water, land and air.
Metal-organic frameworks (MOFs) are promising adsorbents for many guest molecules, although reports concerning adsorption of hydrocarbons (organic vapor) in MOFs remain scarce compared to their H2, CO2, and inert gas adsorption. The high affinity and reactivity of many common MOF materials toward water and humid air largely limits their open-air applications. Thus, the search for water-stable and waterproof (superhydrophobic) MOF materials with the desirable combination of good thermal stability, high selectivity and excellent recyclability is a major challenge and of great technological importance for oil spill cleanup, hydrocarbon storage in a solid matrix to allow transportation in smaller and safer vehicles, catalysis, water purification, component and isomer separation from gasoline mixtures, and environmental remediation of greenhouse gases.